DOCSLIB.ORG

A New Large Deletion Caused by Alu Elements in HEXA

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A New Large Deletion Caused by Alu Elements in HEXA OPEN Citation: Human Genome Variation (2018) 5, 18003; doi:10.1038/hgv.2018.3 Official journal of the Japan Society of Human Genetics www.nature.com/hgv ARTICLE Identification of mutations in HEXA and HEXB in Sandhoff and Tay-Sachs diseases: a new large deletion caused by Alu elements in HEXA Hassan Dastsooz1,3, Mohsen Alipour1,3, Sanaz Mohammadi1, Fatemeh Kamgarpour1, Fatemeh Dehghanian1 and Majid Fardaei1,2 GM2 gangliosides are a group of lysosomal lipid storage disorders that are due to mutations in HEXA, HEXB and GM2A. In our study, 10 patients with these diseases were enrolled, and Sanger sequencing was performed for the HEXA and HEXB genes. The results revealed one known splice site mutation (c.346+1G4A, IVS2+1G4A) and three novel mutations (a large deletion involving exons 6–10; one nucleotide deletion, c.622delG [p.D208Ifsx15]; and a missense mutation, c.919G4A [p.E307K]) in HEXA.InHEXB, one known mutation (c.1597C4T [p.R533C]) and one variant of uncertain significance (c.619A4G [p.I207V]) were identified. Five patients had c.1597C4TinHEXB, indicating a common mutation in south Iran. In this study, a unique large deletion in HEXA was identified as a homozygous state. To predict the cause of the large deletion in HEXA, RepeatMasker was used to investigate the Alu elements. In addition, to identify the breakpoint of this deletion, PCR was performed around these elements. Using Repeat masker, different Alu elements were identified across HEXA, mainly in intron 5 and intron 10 adjacent to the deleted exons. PCR around the Alu elements and Sanger sequencing revealed the start point of a large deletion in AluSz6 in the intron 6 and the end of its breakpoint 73 nucleotides downstream of AluJo in intron 10. Our study showed that HEXA is an Alu-rich gene that predisposes individuals to disease-associated large deletions due to these elements. Human Genome Variation (2018) 5, 18003; doi:10.1038/hgv.2018.3; published online 15 March 2018 INTRODUCTION GM2 ganglioside in the central nervous system, damaging this GM2 gangliosides are a group of lysosomal lipid storage disorders systems and presenting the signs and symptoms identified in that resulted from disease-causing mutations in three autosomal patients with the corresponding disorders. On the basis of the fully recessive genes, including hexosaminidase A (HEXA), hexosamini- nonfunctional HEXA and HEXB proteins or reduced activity of these dase subunit beta (HEXB) and GM2 ganglioside activator (GM2A). proteins resulting from mutations in their genes, these disorders The HEXB gene produces a subunit of two related enzymes that are presented as a severe form found in infancy or a less severe include beta-hexosaminidase A and beta-hexosaminidase B. Both type with a later onset. Tay-Sachs and Sandhoff diseases (which are enzymes have two subunits. Beta-hexosaminidase A is made from clinically indistinguishable from each other) are autosomal one alpha subunit produced from the HEXA gene and one beta recessive, progressive neurodegenerative disorders. Their classical subunit (produced from the HEXB gene). However, beta- infantile forms develop in infancy with developmental retardation, hexosaminidase B is only produced from two beta subunits paralysis, dementia, blindness and death usually by 2 or 3 years of 1,2,4–6 3 encoded from the HEXB gene. Beta-hexosaminidase A and B, age. A study conducted by Smith et al. showed that the which are mainly found in lysosomes, break down sphingolipids, clinical findings in infantile-onset disease were generally as follow: oligosaccharides and glycoproteins, and are critical in the central hyperacusis with excessive startle response in 85% of individuals; nervous system as they have very essential roles in breaking down increased myotatic reflexes in 85% of individuals (children with the GM2 ganglioside in this system, preventing the accumulation infantile-onset disease were not able to walk independently); a of this product and its damage to the nervous system.1–3 pattern of combined axial hypotonia with limb spasticity in 86% of According to the Human Gene Mutation Database (HGMD, individuals; visual deterioration in 89% of individuals; and seizures http://www.hgmd.cf.ac.uk/ac/index.php), more than 182 disease- in 84% of individuals. Considering the importance of identifying causing mutations of the HEXA gene have been identified in genetic causes in our patients that are suggestive of Tay-Sachs and patients affected by Tay-Sachs disease (MIM #272800), including Sandhoff diseases, the aim of our study was to identify disease- missense/nonsense, 96; splicing, 33; small deletions, 28; small causing mutations in these patients from the south of Iran and insertions, 8; small indels, 3; and gross deletions, 1 (7.6 kb incl. report their clinical findings. promoter+ex. 1). Regarding the HEXB gene, to date, more than 107 pathogenic mutations in this gene have been reported in patents affected by Sandhoff disease (MIM #268800), including missense/ MATERIALS AND METHODS nonsense, 39; splicing, 18; small deletion, 18; small insertion, 3; and Ten unrelated patients suspected of GM2 ganglioside diseases from the gross deletion, 6. These mutations result in the accumulation of south of Iran were recruited in the current study. All patients gave 1Comprehensive Medical Genetic Center, Shiraz University of Medical Sciences, Shiraz, Iran and 2Medical Genetics Department, Shiraz University of Medical Sciences, Shiraz, Iran. Correspondence: M Fardaei ([email protected]) 3These authors contributed equally to this work. Received 31 August 2017; revised 21 December 2017; accepted 21 December 2017 New mechanism of genetic mutation in HEXA H Dastsooz et al 2 informed consent before undergoing genetic analysis of the HEXB and fr33.net/translator.php) was used to predict the possible effect of this HEXA genes based on the requirements of the ethics committee in deletion on the amino-acid sequence of the HEXA protein. Comprehensive Medical Genetics Center, Shiraz University of Medical To predict the functional effects and conservation status of a newly Sciences. Three milliliters of whole-blood samples from patients was identified missense mutation in another patient, we also used different collected in EDTA tubes and stored at − 20 °C until use. Genomic DNA was bioinformatics tools, including MutationTaster, MutationAssesor, Polyphen, prepared from peripheral blood lymphocytes using a DNA extraction kit Grantham, PhastCons, GERP, CADD, Fathmm and SIFT. The T-coffee (Yekta Tajhiz, Tehran, Iran) according to the manufacturer’s instructions. multiple sequence alignment program (http://www.ebi.ac.uk/Tools/msa/ The genomic DNA concentration was measured by a NanoDrop (ND1000, tcoffee/) was applied to compare the amino-acid sequence of HEXA NanoDrop Technologies, Wilmington, DE, USA) and stored at –20 °C proteins across different species to obtain information about the until use. conservation of amino acids at the site of mutation. All of the exon and exon–intron boundaries of the HEXA and HEXB genes were amplified by the PCR primers given in Table 1. These primer pairs were designed and evaluated according to their reference genomic RESULTS sequences in ENSEMBLE (https://www.ensembl.org) and the use of NCBI One known (NM_000520 (HEXA-201): c.346+1G4A, IVS2+1G4A)7 BLAST(https://blast.ncbi.nlm.nih.gov), ENSEMBLE BLAST/BLAT (https:// splice site and three novel HEXA mutations, including NM_000520 www.ensembl.org), UCSC (BLAT and In Silico PCR, https://genome.ucsc. 4 – edu) and Allele ID 7.5 (a bioinformatics software that helps design primers (HEXA-201): c.919G A [p.E307K], the deletion of exons 6 10 in a and probes). The total volume of the PCR reaction was 50 μl, which homozygous state and NM_000520 (HEXA-201): c.622delG [p. contained 1 μl of the forward and reverse primers (20 pmol/μl), 3 μl of DNA D208Ifsx15], which are suspected as being homozygous, were template (50–200 ng), 25 μl of TEMPase Hot Start 2x Master Mix Blue identified. One variant of uncertain significance (NM_000521 (Ampicon, A290806) and 20 μl of dH2O. PCR was carried out according to (HEXB-201): c.619A4G [p.I207V])8 and one known mutation the Amplicon TEMPase Hot Start program. Ten microliters of PCR (NM_000521 (HEXB-201):c.1597C4T [p.R533C])9 in HEXB were amplicons were visualized on a 2% agarose gel containing SYBR Safe found in a homozygous state (Table 2). From 10 patients, 5 cases (Invitrogen, Paisley, Scotland, UK). Then, the PCR products were sequenced only had the homozygous p.R533C mutation in HEXB, indicating using Sanger sequencing, and their results were analyzed using NCBI its high frequency in our population. For the first time, a large BLAST and Codon Code Aligner software (CodonCode Corporation, homozygous deletion (deletion of exons 6–10) in HEXA was Centerville, MA, USA). fi In addition, to predict the cause of a new large deletion in the HEXA identi ed in our patient. Using the repeat masker tool, different gene due to Alu elements, RepeatMasker (http://www.repeatmasker.org) Alu elements were found across the HEXA gene (Figure 1), ʹ was used with the RMBlast search engine (a version that was compatible including one Alu at the 5 untranslated region, twelve in intron 1, with the NCBI Blast tool suite). The Repeat masker program screens DNA one in intron 3, four in intron 5 flanking exon 6 (the first exon sequences of interspersed repeats and low complexity DNA sequences. which was deleted in a block of five exon deletions), one in intron Sequence comparisons in RepeatMasker are carried out using one of the 7, one in intron 10 flanking exon 10 (the last exon which was different search engines, including nhmmer, cross_match, ABBlast/ deleted in the deleted block) and three Alus at the 3ʹ untranslated WUBlast, RMBlast and Decypher. RepeatMasker uses information from region. The exact breakpoint of the deletion around exons 6 and curated libraries of repeats, Dfam and Repbase.
Load more

Recommended publications
  • Carrier Screening for Genetic Diseases Policy Number: PG0442 ADVANTAGE | ELITE | HMO Last Review: 07/25/2019
    Carrier Screening for Genetic Diseases Policy Number: PG0442 ADVANTAGE | ELITE | HMO Last Review: 07/25/2019 INDIVIDUAL MARKETPLACE | PROMEDICA MEDICARE PLAN | PPO GUIDELINES This policy does not certify benefits or authorization of benefits, which is designated by each individual policyholder contract. Paramount applies coding edits to all medical claims through coding logic software to evaluate the accuracy and adherence to accepted national standards. This guideline is solely for explaining correct procedure reporting and does not imply coverage and reimbursement. SCOPE X Professional X Facility DESCRIPTION Carrier screening is testing asymptomatic individuals to identify those who are heterozygous for serious or lethal single-gene disorders with the purpose of informing the risk of conceiving an affected child. Risk-based carrier screening is performed in individuals having an increased risk based on population carrier prevalence, and personal or family history. Conditions selected for screening can be based on ethnicities at high risk (e.g., Tay- Sachs disease in individuals of Ashkenazi Jewish descent) or may be pan-ethnic (e.g., screening for cystic fibrosis carriers). Ethnicity-based screening for some conditions has been offered for decades and, in some cases, has reduced the prevalence of diseases. While methods for carrier screening of conditions individually may have been onerous in the past, contemporary molecular techniques including next-generation sequencing allow simultaneously identifying carriers of a wide range of disorders efficiently and inexpensively. Expanded carrier screening (ECS) involves screening individuals or couples for disorders in many genes (up to 100s). The disorders included may also span a range of disease severity or phenotype. Arguments for ECS include potential issues in assessing ethnicity, ability to identify more potential conditions, efficiency, and cost.
    [Show full text]
  • Binding of Undamaged Double Stranded DNA to Vaccinia Virus
    Schormann et al. BMC Structural Biology (2015) 15:10 DOI 10.1186/s12900-015-0037-1 RESEARCH ARTICLE Open Access Binding of undamaged double stranded DNA to vaccinia virus uracil-DNA Glycosylase Norbert Schormann1, Surajit Banerjee2, Robert Ricciardi3 and Debasish Chattopadhyay1* Abstract Background: Uracil-DNA glycosylases are evolutionarily conserved DNA repair enzymes. However, vaccinia virus uracil-DNA glycosylase (known as D4), also serves as an intrinsic and essential component of the processive DNA polymerase complex during DNA replication. In this complex D4 binds to a unique poxvirus specific protein A20 which tethers it to the DNA polymerase. At the replication fork the DNA scanning and repair function of D4 is coupled with DNA replication. So far, DNA-binding to D4 has not been structurally characterized. Results: This manuscript describes the first structure of a DNA-complex of a uracil-DNA glycosylase from the poxvirus family. This also represents the first structure of a uracil DNA glycosylase in complex with an undamaged DNA. In the asymmetric unit two D4 subunits bind simultaneously to complementary strands of the DNA double helix. Each D4 subunit interacts mainly with the central region of one strand. DNA binds to the opposite side of the A20-binding surface on D4. Comparison of the present structure with the structure of uracil-containing DNA-bound human uracil-DNA glycosylase suggests that for DNA binding and uracil removal D4 employs a unique set of residues and motifs that are highly conserved within the poxvirus family but different in other organisms. Conclusion: The first structure of D4 bound to a truly non-specific undamaged double-stranded DNA suggests that initial binding of DNA may involve multiple non-specific interactions between the protein and the phosphate backbone.
    [Show full text]
  • Low Levels of 18 Hexosaminidase a in Healthy Individuals with Apparent Deficiency of This Enzyme
    Am J Hum Genet 28:339-349, 1976 Low Levels of 18 Hexosaminidase A in Healthy Individuals with Apparent Deficiency of This Enzyme R. NAVON,1 B. GEIGER,2 Y. BEN YOSEPH,2 AND M. C. RATTAZZI3 INTRODUCTION The association between Tay-Sachs disease (TSD; GM,2 gangliosidosis type I) and generalized deficiency of /8 hexosaminidase A (hex A) activity with artificial sub- strates, first reported by Okada and O'Brien [1], is now well established. Using natural substrates, it has also been shown that tissues from patients with TSD cannot degrade GM2 ganglioside in vitro [2, 3] and that purified hex A, but ap- parently not purified /f hexosaminidase B (hex B), can hydrolyze GM2 ganglioside to a measurable extent [3, 4]. Thus, hex A deficiency is commonly believed to be the cause of the accumulation of GM2 ganglioside in patients with TSD. However, it has recently been reported that purified hex B can cleave GM2 ganglioside in vitro [5], raising the question of its participation in the catabolism of this glyco- lipid in vivo. In a recent publication [6], Navon et al. described a Jewish family in which four healthy adult individuals showed a severe deficiency of hex A activity. Using a heat inactivation method based on the differential thermal lability of hex A and hex B [7, 8], it was shown that, in these subjects, hex A activity with artificial substrates was comparable to that of patients with TSD [6]. Further studies em- ploying radioactive natural substrates, however, showed that leukocytes from these "variant" individuals were capable of hydrolysis of GA12 ganglioside in vitro [9].
    [Show full text]
  • GM2 Gangliosidoses: Clinical Features, Pathophysiological Aspects, and Current Therapies
    International Journal of Molecular Sciences Review GM2 Gangliosidoses: Clinical Features, Pathophysiological Aspects, and Current Therapies Andrés Felipe Leal 1 , Eliana Benincore-Flórez 1, Daniela Solano-Galarza 1, Rafael Guillermo Garzón Jaramillo 1 , Olga Yaneth Echeverri-Peña 1, Diego A. Suarez 1,2, Carlos Javier Alméciga-Díaz 1,* and Angela Johana Espejo-Mojica 1,* 1 Institute for the Study of Inborn Errors of Metabolism, Faculty of Science, Pontificia Universidad Javeriana, Bogotá 110231, Colombia; [email protected] (A.F.L.); [email protected] (E.B.-F.); [email protected] (D.S.-G.); [email protected] (R.G.G.J.); [email protected] (O.Y.E.-P.); [email protected] (D.A.S.) 2 Faculty of Medicine, Universidad Nacional de Colombia, Bogotá 110231, Colombia * Correspondence: [email protected] (C.J.A.-D.); [email protected] (A.J.E.-M.); Tel.: +57-1-3208320 (ext. 4140) (C.J.A.-D.); +57-1-3208320 (ext. 4099) (A.J.E.-M.) Received: 6 July 2020; Accepted: 7 August 2020; Published: 27 August 2020 Abstract: GM2 gangliosidoses are a group of pathologies characterized by GM2 ganglioside accumulation into the lysosome due to mutations on the genes encoding for the β-hexosaminidases subunits or the GM2 activator protein. Three GM2 gangliosidoses have been described: Tay–Sachs disease, Sandhoff disease, and the AB variant. Central nervous system dysfunction is the main characteristic of GM2 gangliosidoses patients that include neurodevelopment alterations, neuroinflammation, and neuronal apoptosis. Currently, there is not approved therapy for GM2 gangliosidoses, but different therapeutic strategies have been studied including hematopoietic stem cell transplantation, enzyme replacement therapy, substrate reduction therapy, pharmacological chaperones, and gene therapy.
    [Show full text]
  • Hexosaminidase a in Tay–Sachs Disease
    Journal of Genetics (2020)99:42 Ó Indian Academy of Sciences https://doi.org/10.1007/s12041-020-01208-8 (0123456789().,-volV)(0123456789().,-volV) RESEARCH ARTICLE In silico analysis of the effects of disease-associated mutations of b-hexosaminidase A in Tay–Sachs disease MOHAMMAD IHSAN FAZAL1, RAFAL KACPRZYK2 and DAVID J. TIMSON3* 1Brighton and Sussex Medical School, University of Sussex, Falmer, Brighton BN1 9PX, UK 2School of Biological Sciences, Queen’s University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK 3School of Pharmacy and Biomolecular Sciences, University of Brighton, Huxley Building, Lewes Road, Brighton BN2 4GJ, UK *For correspondence. E-mail: [email protected]. Received 6 September 2019; revised 25 February 2020; accepted 24 April 2020 Abstract. Tay–Sachs disease (TSD), a deficiency of b-hexosaminidase A (Hex A), is a rare but debilitating hereditary metabolic disorder. Symptoms include extensive neurodegeneration and often result in death in infancy. We report an in silico study of 42 Hex A variants associated with the disease. Variants were separated into three groups according to the age of onset: infantile (n=28), juvenile (n=9) and adult (n=5). Protein stability, aggregation potential and the degree of conservation of residues were predicted using a range of in silico tools. We explored the relationship between these properties and the age of onset of TSD. There was no significant relationship between protein stability and disease severity or between protein aggregation and disease severity. Infantile TSD had a significantly higher mean con- servation score than nondisease associated variants. This was not seen in either juvenile or adult TSD.
    [Show full text]
  • O-Glcnacase Fragment Discovery with Fluorescence Polarimetry
    Articles Cite This: ACS Chem. Biol. 2018, 13, 1353−1360 O‑GlcNAcase Fragment Discovery with Fluorescence Polarimetry Vladimir S. Borodkin,*,†,∥ Karim Rafie,†,∥ Nithya Selvan,†,§,∥ Tonia Aristotelous,‡ Iva Navratilova,‡ Andrew T. Ferenbach,† and Daan M. F. van Aalten*,† † ‡ Centre for Gene Regulation and Expression and Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, United Kingdom *S Supporting Information ABSTRACT: The attachment of the sugar N-acetyl-D-glucosamine (GlcNAc) to specific serine and threonine residues on proteins is referred to as protein O-GlcNAcylation. O-GlcNAc transferase (OGT) is the enzyme responsible for carrying out the modification, while O-GlcNAcase (OGA) reverses it. Protein O-GlcNAcylation has been implicated in a wide range of cellular processes including transcription, proteostasis, and stress response. Dysregulation of O-GlcNAc has been linked to diabetes, cancer, and neurodegenerative and cardiovascular disease. OGA has been proposed to be a drug target for the treatment of Alzheimer’s and cardiovascular disease given that increased O-GlcNAc levels appear to exert a protective effect. The search for specific, potent, and drug-like OGA inhibitors with bioavailability in the brain is therefore a field of active research, requiring orthogonal high-throughput assay platforms. Here, we describe the synthesis of a novel probe for use in a fluorescence polarization based assay for the discovery of inhibitors of OGA. We show that the probe is suitable for use with both human OGA, as well as the orthologous bacterial counterpart from Clostridium perfringens, CpOGA, and the lysosomal hexosaminidases HexA/B. We structurally characterize CpOGA in complex with a ligand identified from a fragment library screen using this assay.
    [Show full text]
  • In-Silico Chaperone Model for ATSD and Case Study
    CASE REPORT OF CHAPERONE THERAPY FOR ADULT TAY-SACHS DISEASE AND COMPARISON TO AN IN-SILICO PHARMACOKINETIC AND CELLULAR SIMULATION John G. (Jack) Keimel and Lawrence Charnas MD PhD, University of Minnesota, Minneapolis, Minnesota ABSTRACT CELLULAR MODELS CELLULAR SIMULATION RESULTS CASE STUDY OF PYRIMETHAMINE IN AN ATSD PATIENT Background: Individuals with Adult Tay-Sachs Disease (ATSD) Model 2: Model 3: Model Calibration: Patient History: Drug Regimen: develop ataxia and dysarthria by early teenage years and later lose Endoplasmic Reticulum Lysosome A single constant calibration factor, “cal”, sets the translation rate of α, A male confirmed with ATSD (alpha mutations: +1IVS12 (G>C) and At the request of the patient and parents, pyrimethamine ability to walk. No therapy has yet been shown clinically effective. α , and β HexA monomers. The factor was chosen such that, for Dimer Formation GM2 GM2 Degradation m G269S ) had been taking a substrate reduction therapy, miglustat, (PYR) 25mg QD was begun for two weeks followed by 75mg ATSD is caused by inadequate β-hexosaminidase-A (HexA) activity normal individuals with no PYR present, the steady state lysosomal for greater than four years, but at age 25 showed accelerated QD for eight weeks. Folic acid (5mg QD) was initiated with the and GM2 ganglioside accumulation in neuronal lysosomes. The concentration of HexA is equal to the above calculated value of 25μM. decline in coordination and leg muscle strength, verified by EMG first dose of PYR to offset partial dihydrofolate reductase most prevalent ATSD mutation, αG269S, is not believed to impact [PYR] [PYR] αβ evaluations. The patient lost the ability to climb stairs and required inhibition caused by PYR.
    [Show full text]
  • Oxidative Demethylation of DNA Damage by Escherichia Coli Alkb
    Oxidative déméthylation of DNA damage by Escherichia coli AlkB and its human homologs ABH2 and ABH3 A thesis submitted for the degree of Ph D. by Sarah Catherine Trewick Clare Hall Laboratories Cancer Research UK London Research Institute South Mimms, Potters Bar Hertfordshire, EN6 3LD and Department of Biochemistry University College London Gower Street, London, WCIE 6BT ProQuest Number: U642489 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest U642489 Published by ProQuest LLC(2015). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. Microform Edition © ProQuest LLC. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 ABSTRACT The E. coli AlkB protein was implicated in the repair or tolerance of DNA méthylation damage. However, despite the early isolation of an E. coli alkB mutant, the function of the AlkB protein had not been resolved (Kataoka et al, 1983). The E. coli alkB mutant is defective in processing methylated single stranded DNA, therefore, it was suggested that the AlkB protein either repairs or tolerates lesions generated in single stranded DNA, such as 1-methyladenine (1-meA) or 3-methylcytosine (3-meC), or that AlkB only acts on single stranded DNA (Dinglay et al, 2000).
    [Show full text]
  • Impaired Β-Glucocerebrosidase Activity and Processing in Frontotemporal Dementia Due to Progranulin Mutations Andrew E
    Arrant et al. Acta Neuropathologica Communications (2019) 7:218 https://doi.org/10.1186/s40478-019-0872-6 RESEARCH Open Access Impaired β-glucocerebrosidase activity and processing in frontotemporal dementia due to progranulin mutations Andrew E. Arrant1,2*, Jonathan R. Roth1, Nicholas R. Boyle1, Shreya N. Kashyap1, Madelyn Q. Hoffmann1, Charles F. Murchison1,3, Eliana Marisa Ramos4, Alissa L. Nana5, Salvatore Spina5, Lea T. Grinberg5,6, Bruce L. Miller5, William W. Seeley5,6 and Erik D. Roberson1,7* Abstract Loss-of-function mutations in progranulin (GRN) are a major autosomal dominant cause of frontotemporal dementia. Most pathogenic GRN mutations result in progranulin haploinsufficiency, which is thought to cause frontotemporal dementia in GRN mutation carriers. Progranulin haploinsufficiency may drive frontotemporal dementia pathogenesis by disrupting lysosomal function, as patients with GRN mutations on both alleles develop the lysosomal storage disorder neuronal ceroid lipofuscinosis, and frontotemporal dementia patients with GRN mutations (FTD-GRN) also accumulate lipofuscin. The specific lysosomal deficits caused by progranulin insufficiency remain unclear, but emerging data indicate that progranulin insufficiency may impair lysosomal sphingolipid- metabolizing enzymes. We investigated the effects of progranulin insufficiency on sphingolipid-metabolizing enzymes in the inferior frontal gyrus of FTD-GRN patients using fluorogenic activity assays, biochemical profiling of enzyme levels and posttranslational modifications, and quantitative neuropathology. Of the enzymes studied, only β-glucocerebrosidase exhibited impairment in FTD-GRN patients. Brains from FTD-GRN patients had lower activity than controls, which was associated with lower levels of mature β-glucocerebrosidase protein and accumulation of insoluble, incompletely glycosylated β-glucocerebrosidase. Immunostaining revealed loss of neuronal β- glucocerebrosidase in FTD-GRN patients.
    [Show full text]
  • Carrier Detection for Tay-Sachs Disease: a Model for Genetic Disease Prevention
    Carrier detection for Tay-Sachs disease: a model for genetic disease prevention Irene De Biase, MD PhD Assistant Professor of Pathology, University of Utah Assistant Medical Director, Biochemical Genetics and Supplemental Newborn Screening, ARUP Laboratories Conflict of Interest . None to declare Learning objectives . Review the clinical characteristics and the biochemical features of Tay-Sachs Disease . Describe the population-based screening for Tay-Sachs disease and its impact on disease incidence . Explore the unique challenges in carrier testing for Tay-Sachs disease Cherry red spot Warren Tay British ophthalmologist In 1881, he described the cherry red spot on the retina of a one-year old child with mental and physical retardation NOVEL collection University of Utah Bernard Sachs Jewish-American neurologist In 1896, observed the extreme swelling of neurons in autopsy tissue of affected children Also noticed the disease seemed to be of Jewish origin TSD is a lysosomal storage disease . The underlying biochemical defect is the profound deficiency of the lysosomal hydrolase b-hexosaminidase A . HexA is necessary for the break-down of the ganglioside GM2, a component of the plasma membrane Okada et al. Science 1969; 165:698-700 Degradation of glycosphingolipids GM2 Generalized Gangliosidosis GA2 Sandhoff Disease Tay-Sachs Disease Fabry Disease Metachromatic leukodystrophy Gaucher Disease Krabbe Disease Essentials of Glycobiology Second Edition b-hexosaminidase isoforms: HexA and HexB GM2 Generalized Gangliosidosis GA2 Tay-Sachs Disease HexB: ββ Sandhoff Disease GM2 HexA: αβ activator Fabry Disease GM2 activator Metachromatic leukodystrophy Gaucher Disease Krabbe Disease Essentials of Glycobiology Second Edition Three gene system required for HexA activity 1. 2.
    [Show full text]
  • A Novel Uracil-DNA Glycosylase Family Related to the Helix±Hairpin±Helix DNA Glycosylase Superfamily
    Nucleic Acids Research, 2003, Vol. 31, No. 8 2045±2055 DOI: 10.1093/nar/gkg319 A novel uracil-DNA glycosylase family related to the helix±hairpin±helix DNA glycosylase superfamily Ji Hyung Chung1,2,3, Eun Kyoung Im2,3, Hyun-Young Park1,2,3, Jun Hye Kwon2,4, Seahyoung Lee2, Jaewon Oh2, Ki-Chul Hwang2,3, Jong Ho Lee1,2,3 and Yangsoo Jang1,2,3,4,* 1Yonsei Research Institute of Aging Science, 2Cardiovascular Research Institute, 3Cardiovascular Genome Center and 4Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Yonsei University, Seoul, 120-752, Korea Received January 23, 2003; Revised and Accepted February 21, 2003 ABSTRACT catalyze the major repair process, the base excision repair (BER) pathway, which is initiated by removal of the damaged Cytosine bases can be deaminated spontaneously base (2,3). Among those DNA glycosylases, uracil-DNA to uracil, causing DNA damage. Uracil-DNA glyco- glycosylase (UDG) was the ®rst to be discovered (4), and it sylase (UDG), a ubiquitous uracil-excising enzyme acts as a major repair enzyme that protects DNA from found in bacteria and eukaryotes, is one of the mutational damages caused by the misincorporation of uracil enzymes that repair this kind of DNA damage. To due to a polymerase error or deamination of cytosine. This date, no UDG-coding gene has been identi®ed in repair enzyme hydrolyzed the N-glycosidic bond. As a result, Methanococcus jannaschii, although its entire uracil base is released from the DNA backbone, leaving an genome was deciphered. Here, we have identi®ed abasic site behind.
    [Show full text]
  • An Unusual Splicing Mutation in the HEXB Gene Is Associated with Dramatically Different Phenotypes in Patients from Different Racial Backgrounds
    An unusual splicing mutation in the HEXB gene is associated with dramatically different phenotypes in patients from different racial backgrounds. B McInnes, … , S Tsuji, D J Mahuran J Clin Invest. 1992;90(2):306-314. https://doi.org/10.1172/JCI115863. Research Article Sandhoff disease is caused by mutations affecting the beta subunit of lysosomal beta-hexosaminidase (EC 3.2.1.52) and displays a wide spectrum of clinical phenotypes. We report a 57-year-old patient with a very mild phenotype, although residual hexosaminidase A activity in his cultured fibroblasts was less than 3% of normal activity, a level observed in juvenile onset patients. Northern and Western blot analyses confirmed a similar low level of beta subunit-mRNA and mature beta-protein, respectively. Two mutations of the HEXB gene were identified in this patient, a partial 5' gene deletion (a null allele), and a C----T transition 8 nucleotides downstream from the intron 10/exon 11 junction affecting the splicing of the beta subunit-mRNA. In their homozygous forms, the 5' deletion has been previously shown to result in a severe infantile phenotype, and the C----T transition in a juvenile phenotype. The genotype and the low level of residual hexosaminidase A activity would be expected to produce a juvenile Sandhoff phenotype in this patient, as well as in four of his six clinically normal siblings. The biochemical basis of his mild phenotype is uncertain, but may result from genetic variations in the RNA splicing machinery. Find the latest version: https://jci.me/115863/pdf An Unusual Splicing Mutation in the HEXB Gene Is Associated with Dramatically Different Phenotypes in Patients From Different Racial Backgrounds Beth McInnes, * Michel Potier,t1 Nobuaki Wakamatsu,11 Serge B.
    [Show full text]